The present invention relates to aqueous colorants; for keratin fibers, and more particularly, to compositions for dyeing pelts and human hair. In a further aspect, the present invention relates to a method for coloring pelts and human hair and to the products obtained thereby.
The so-called oxidation dyes, which are formed by oxidative coupling of developer components (such as e.g. p-phenylenediamines, p-aminophenols or p-diaminopyridines) with coupling components (such as e.g. phenols, resorcinols, m-aminophenols, m-phenylenediamines, naphthols or pyrazolones), have particular importance for the coloration of hair. Even when used under marginal conditions (low dyeing temperature and short dyeing period), they afford intense dyeings having very good fastness. The oxidation dyes likewise play an important role in the dyeing of pelts.
Good oxidation dyes must primarily fulfill the following utilization requirements: during oxidative coupling with the particular coupling or developer component, they must afford the desired coloration, which should have a good absorption and leveling ability on the hair or pelts, in adequate intensity. The dyes formed must generally be stable and especially posses good wash-fastness and light-fastness. They must also be perspiration-resistant and heat-stable. In particular, under actual wear conditions they must not be prone to color changes of the original shade. Moreover, they should be toxicologically and dermatologically acceptable.
Aqueous colorants for keratin fibers based on oxidation dye precursors are described by Karlheinz Schrader, "Grundlagen und Rezepturen der Kosmetika" [Foundations and Formulations for Cosmetics], 2nd revised and extended edition, Huethig Buch Verlag, Heidelberg 1989, pages 782 to 815; Hair Coloring, Rev. Prog. Coloration, Vol. 15, 52 ff (1985); J. F. Corbett, The Chemistry of Synthetic Dyes, Vol. 5, edited by Venkataraman, Academic Press, New York and London, 1971.
A requirement for oxidative dyeing, however, is that the oxidation dye precursors must be able to penetrate into the hair. In order to guarantee this, alkalis, preferably ammonia, are added to the hair colorants. As a result of the oxidizing agent, which is not only used for the coupling of the dye precursors, but also destroys the melanin of the hair, and as a result of the alkali, in particular as a result of the ammonia, the hair is appreciably damaged during dyeing. As a result, the hair can be harder to comb. In order to solve this problem, after dyeing the hair is often treated with a shampoo and with a conditioner in two further working steps. This, however, is labor-intensive and does not always lead to satisfactory results.
It is therefore an object of the present invention to find formulations containing specific constituents which are less harsh on the condition of the hair during and after oxidative dyeing.